The present invention relates to a method and device for controlling a hybrid automobile in which only a drive force of a motor is outputted to wheels by stopping an engine but operating the motor when a required drive force is below a predetermined switch value, and on the other hand, a drive force of at least the engine is outputted to the wheels by operating at least the engine when the required drive force is above the predetermined switch value.
Recently, hybrid automobiles provided with engines and motors as drive sources of the vehicles have been disclosed. For example, JP2004-092428A discloses such a hybrid automobile in which a motor travel and an engine travel are switched therebetween according to a required drive force. In the motor travel, the engine is stopped but the vehicle travels only by a drive force of the motor, and in the engine travel, the engine is operated and the vehicle travels by a drive force of the engine (note that, the drive force of the motor may also be used).
Since engines of such hybrid automobiles are operated intermittently while traveling, emission performance may degrade. For example, JP2004-092428A also discloses an art for suppressing an emission degradation when a catalyst temperature is decreased during the motor travel and an activation of the catalyst is required to maintain an activated state of the catalyst in preparation of switching to the engine travel, by retarding an ignition timing of the engine to activate the catalyst rapidly while operating the engine in a no-load state by releasing clutches arranged on a drive path between the engine and drive wheels.
However, with the art disclosed in JP2004-092428A, as described above, when the activation of the catalyst is required during the motor travel, the ignition timing of the engine is retarded while operating the engine in the no-load state. Therefore, the required drive force does not increase. When the motor travel continues, even though there is no risk of emission degradation, a consumption amount of fuel increases unnecessarily, causing a problem of fuel consumption degradation.